These studies of brain tissue transplantation in non-primate animals attempt (1) to develop the techniques of brain tissue transplantation so that it may be applied clinically to Parkinson's disease, (2) to develop brain tissue transplantation techniques for eventual application to other disorders, such as schizophrenia or Alzheimer's disease if and when these disorders become well enough understood to permit such applications, and (3) to employ brain tissue transplanatation as a technique to elucidate factors which control the development and plasticity of the brain, particularly the nigrostriatal dopamine system. During the past reporting year important progress has been made toward achieving these goals.